This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Small-angle x-ray scattering (SAXS) provides information about the shapes of molecules and assemblies. The shape information is limited, being just scattering intensity as a function of angle averaged over all molecule orientations. But the ability to probe the shape in native-like liquid conditions, with quick data acquisition, simple sample preparation, and control of conditions (pH, ions, drugs, temperature) makes this a powerful technique to study structure and dynamics. Interpretation of SAXS data is the main difficulty in using this technique. This project develops software to explore the degree of agreement between atomic models and SAXS profiles using the interactive UCSF Chimera visualization software. Interactive visualization is well-suited for analysis of this data because scattering profiles can be calculated from molecular models in seconds and compared to experimental results to explore the ambiguity inherent in SAXS data.